Nitride semiconductors are used in various semiconductor devices such as semiconductor light emitting devices and HEMT (high electron mobility transistor) devices. However, the characteristics of such nitride semiconductor devices are restricted by high-density threading dislocations due to lattice mismatch with the GaN crystal.
For example, one of the semiconductor light emitting devices based on nitride semiconductors is a near ultraviolet LED (light emitting diode) device (for example, the emission wavelength is, e.g., 400 nm or shorter). The near ultraviolet LED is expected to serve as a phosphor-exciting light source for white LED and the like. However, it has the problem of low efficiency.
Various proposals have been made to increase the efficiency of the near ultraviolet LED based on nitride semiconductors. For example, Japanese Patent No. 2713094 proposes a configuration for controlling the condition for various layers included in the semiconductor light emitting device. However, there is room for improvement in increasing the efficiency of the near ultraviolet LED.